Copolyester-carbonate resins having pendant carboxyl groups derived from polycarboxylic acid monoesters and crosslinked products therefrom

ABSTRACT

Thermoplastic copolyester-carbonate resins are described, having included in their polymer chains, a moiety of the formula: ##STR1## The resins are useful intermediates for branched or cross-linked molding compositions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to polycarbonate resins and more particularlyrelates to branched or cross-linked copolyester-carbonate resins andintermediates thereto.

2. Brief Description of the Prior Art

Polycarbonate resins have found wide usage to fabricate a wide varietyof articles such as automotive component parts.

A wide variety of copolyester-carbonate resins are also known in theprior art as is the method of their preparation; see for example U.S.Pat. No. 4,487,896.

SUMMARY OF THE INVENTION

The invention comprises a copolyester-carbonate resin, containing in thepolymer chain at least one divalent moiety of the formula: ##STR2##wherein a and b are each whole number integers of from 0 to 1; and thesum of a +b is 1.

The copolyester-carbonates of the invention are useful as intermediatesin the preparation of branched or cross-linked polycarbonate moldingresins and as branching or cross-linking additives in polycarbonate andcopolyester-carbonate resin compositions

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The copolyester-carbonate resins of the invention, i.e.; the resinscontaining a unit of formula (I), may be prepared by the thermolyticdegradation of corresponding copolyester-carbonate resins prepared bythe reaction of a carbonate precursor, a dihydric phenol, and adicarboxylic acid or mixture of dicarboxylic acids selected from thoseof the formulae: ##STR3## wherein R, is a hydrocarbyl group which isamenable to beta-elimination upon exposure to heat. Rather than usingthe diacids of the formulae IIA and IIB, it is possible to also use thereactive derivatives of those acids, i.e., the acid halides such as theacid dichlorides or the acid dibromides. Also, these reactivederivatives may be prepared in-situ during the polymerization reactionfrom the diacids of the formulae IIA and IIB. The preparative reactionwith acids (IIA) and (IIB) or their reactive derivatives is carried outunder conditions to produce a copolyester-carbonate resin. Such reactionconditions are well known to those skilled in the art of polycarbonatepolymer resins and are described, for example, in the U.S. Pat. Nos.3,028,365; 3,334,154; 3,275,601; 3,915,926; 3,030,331; 3,169,121; 3,027814; and 4,188,314. In general, the preparation may be carried out byinterfacial polymerization or phase boundary separation, solutionpolymerization and like processes. Interfacial polymerization ispreferred.

Although the preparative processes may vary, several of the preferredprocesses typically involve dissolving or dispersing the reactants in asuitable water immiscible solvent medium and contacting the reactantswith a carbonate precursor, such as phosgene, in the presence of asuitable catalyst and an aqueous caustic solution under controlled pHconditions. A molecular weight regulator, that is a chain stopper, maybe added to the reactants prior to or during contacting them with acarbonate precursor. Useful molecular weight regulators include, but arenot limited to, monohydric phenols such as phenol, chroman-I,paratertiarybutylphenol, and the like. Techniques for the control ofmolecular weight are well known in the art and may be used in thepresent process for controlling the molecular weight of thecopolyester-carbonate resins. The most commonly used water immisciblesolvents include methylene chloride, 1,2-dichloroethane, chlorobenzene,toluene, and the like.

The catalysts which can be employed, if an interfacial polymerizationtechnique is used, accelerate the rate of polymerization of the dihydricphenol reactant with the ester precursor such as the dicarboxylic acidand with the carbonate precursor such as phosgene. Suitable catalystsinclude but are not limited to tertiary amines such as triethylamine,quaternary phosphonium compounds, quaternary ammonium compounds, and thelike.

The preferred process comprises a phosgenation reaction. The temperatureat which the phosgenation reaction proceeds may vary from below 0° C.,to above 100° C. The reaction preferably proceeds at temperatures offrom room temperature (25° C.) to 50° C. Since the reaction isexothermic, the rate of phosgene addition may be used to control thereaction temperature. The amount of the phosgene required will generallydepend upon the amount of the dihydric phenol present. Generallyspeaking, one mole of phosgene will react with one mole of the dihydricphenol to provide the polymer and two moles of HCl. Two moles of HCl arein turn "attached" by an acid acceptor, preferably present. Theforegoing are herein referred to as stoichiometric or theoreticalamounts.

A suitable acid acceptor present in the reaction mixture may be eitherorganic or inorganic in nature. Representative of an organic acidacceptor is a tertiary amine such as pyridine, triethylamine,dimethylaniline, tributylamine, etc. An inorganic acid acceptor may beone which can be either a hydroxide, a carbonate, a bicarbonate, or aphosphate or an alkali or alkaline earth metal hydroxide.

Dihydric phenol reactants employed to prepare thecopolyester-polycarbonate resins subjected to thermal degradation toobtain resins of the invention are generally well known compounds as aremethods of their preparation. Representative of such dihydric phenolsare phenolic diols of the general formula: ##STR4## wherein A isselected from the group consisting of a divalent hydrocarbon containingfrom 1 to about 15 carbon atoms; a substituted divalent hydrocarbonradical containing from 1 to about 15 carbon atoms and substituentgroups such as halogen; ##STR5## and wherein each X is independentlyselected from the group consisting of halogen, a monovalent hydrocarbonradical such as an alkyl group of from 1 to about 8 carbon atoms, anaryl group of from 6-18 carbon atoms, an aralkyl group of from 7 toabout 14 carbon atoms, an oxyalkyl group of from 1 to about 8 carbonatoms, and an oxyaryl group of from 6 to 18 carbon atoms; and wherein mis zero or 1 and y is a whole number integer of from 0 to 4.

Typical of some of the dihydric phenols that can be advantageouslyemployed in the practice of the present invention are bis-phenols suchas bis(4-hydroxyphenyl)methane, 2,2-bis(4-hydroxyphenyl)propane (alsoknown as bisphenol A), 2,2-bis(4-hydroxy-3-methylphenyl)propane,4,4-bis(4-hydroxyphenyl)heptane,2,2bis(4-hydroxy-3,5-dichlorophenyl)propane,2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, etc.; dihydric phenolethers such as bis(4-hydroxyphenyl)ether,bis(3,5-dichloro-4-hydroxyphenyl)ether, etc.; dihydroxydiphenyls such asp,p'-dihydroxydiphenyl, 3,3-dichloro-4,4'-dihydroxydiphenyl, etc.;dihydroxyaryl sulfones such as bis(4-hydroxyphenyl) sulfone,bis(3,5-dimethyl-4-hydroxyphenyl)sulfone, etc.; dihydroxy benzenes,resorcinol, hydroquinone, halo- and alkyl-substituted dihydroxy benzenessuch as 1,4-dihydroxy-2,5-dichlorobenzene,1,4-dihydroxy-3-methylbenzene, etc.; and dihydroxy diphenyl sulfides andsulfoxides such as bis(4-hydroxyphenyl)sulfide andbis(4-hydroxyphenyl)sulfoxide,bis(3,5-dibromo-4-hydroxyphenyl)sulfoxide, etc. A variety of additionaldihydric phenols are also available and are disclosed in U.S. Pat. Nos.2,999,835; 3,028,365 and 3,153,008, all of which are incorporated hereinby reference. It is, of course, possible to employ two or more differentdihydric phenols or a combination of a dihydric phenol with glycol.

Preferred dihydric phenols of Formula (III) are the 4,4'-bisphenols.

The carbonate precursor employed in the preparation of the polycarbonateand polyester-carbonate subjected to thermal degradation to prepare theresins of the invention may be a carbonyl halide, a diarylcarbonate, ora bishaloformate. The carbonyl halides include carbonyl bromide,carbonyl chloride, and mixtures thereof. The bishaloformates include thebishaloformates of dihydric phenols such as bischloroformates ofdihydric phenols such as bischloroformates of2,2-bis(4-hydroxyphenyl)propane, hydroquinone, and the like; or thebischloroformates of glycols such as the bischloroformates of neopentylglycol and the like.

The preferred carbonate precursors are the carbonyl halides, withcarbonyl chloride, also known as phosgene, being the preferred carbonylhalide

Dicarboxylic acids of the formula (II) given above may be prepared bythe reaction of trimellitic anhydride (IV) with an aliphatic alcohol (V)according to the schematic formulae: ##STR6## wherein R has the meaningpreviously ascribed to it. Preferably R represents an alkyl or acycloalkyl group amenable to removal by thermal degradation.

The terms "alkyl" and "cycloalkyl" as used herein means the monovalentmoiety obtained upon removal of one hydrogen atom from a parentaliphatic hydrocarbon. Representative of alkyl is ethyl, propyl,n-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and isomeric formsthereof. Representative of cycloalkyl are cyclopentyl and cyclohexyl.

The above-illustrated reaction for preparation of the isomers offormulae (IIA) and (IIB) may be carried out by mixing stoichiometricproportions of the reactants (IV) and (V) and heating the mixture,preferably to a temperature of circa 100° C. to 200° C. either neat orin the presence of an inert organic solvent. The term "inert organicsolvent" as used herein means an organic solvent for the reactants whichdoes not enter into reaction with the reactants (IV) or (V) or adverselyaffect the desired course of the reaction. Representative of inertorganic solvents are methyl ethyl ketone, methyl isobutyl ketone and thelike. The general procedure for the preparation of the Compounds (II) iswell known and may be found, for example, in U.S. Pat. No. 3,578,638.

Aliphatic alcohols of the formula (V) given above are well knowncompounds as are methods of their preparation. Representative ofaliphatic alcohols of the formula (V) are isopropyl alcohol and thelike.

In addition to the dicarboxylic acids of formula (II) given above, thepolyester-carbonate resins subjected to thermal degradation to obtainthe resins of the invention may optionally contain reaction residues ofother difunctional carboxylic acids, conventionally used in thepreparation of copolyester-polycarbonate resins. In general, anydifunctional carboxylic acid conventionally used in the preparation oflinear polyesters may optionally be utilized in the preparation of thecopolyester-carbonate resins of the instant invention. Generally, thecarboxylic acids which may be optionally utilized include the aliphaticcarboxylic acids, the aromatic carboxylic acids, and thealiphaticaromatic carboxylic acids. These acids are well known and aredisclosed in U.S. Pat. No. 3,169,121, which is hereby incorporatedherein by reference. Representative of such difunctional carboxylicacids are difunctional carboxylic acids of the formula: ##STR7## whereinR⁵ is an alkylene, alkylidene, or cycloaliphatic group; an alkylene,alkylidene or cycloaliphatic group containing ethylenic unsaturation; anaromatic group such as phenylene, biphenylene, and the like; two or morearomatic groups connected through non-aromatic linkages such as alkyleneor alkylidene groups; and a divalent aralkyl radical such as tolylene,xylylene, and the like. R⁴ is either a carboxyl or a hydroxyl group. Theletter q represents one where R⁴ is a hydroxyl group and either zero orone where R⁴ is a carboxyl group.

Preferred difunctional carboxylic acids optionally employed are thearomatic dicarboxylic acids. Particularly useful aromatic dicarboxylicacids are those represented by the general formula: ##STR8## wherein jis a positive whole integer having a value of from 0 to 4 inclusive; andR⁶ is independently selected from the group consisting of alkylradicals, preferably lower alkyl radicals containing from 1 to about 5carbon atoms.

Mixtures of these optional difunctional carboxylic acids may be employedas well as single acids. Therefore, where the term difunctionalcarboxylic acid is used herein it is to be understood that this termincludes mixtures of two or more different difunctional carboxylic acidsas well as individual carboxylic acids.

Preferred optional aromatic dicarboxylic acids are isophthalic acid,terephthalic acid, and mixtures thereof. A particularly usefulcarboxylic acid comprises a mixture of isophthalic acid and terephthalicacid wherein the weight ratio of terephthalic acid to isophthalic acidis in the range of from about 9:1 to about 0.2:9.8.

Rather than utilizing the optional difunctional carboxylic acid per se,it is possible, and sometimes even preferred, to employ the reactivederivatives of said acid. Illustrative of these reactive derivatives arethe acid halides. The preferred acid halides are the acid dichloridesand the acid dibromides. Thus, for example, instead of using isophthalicacid, terephthalic acid, or mixtures thereof, it is possible to employisophthaloyl dichloride, terephthaloyl dichloride, and mixtures thereof.

Also included within the scope of the instant invention are randomlybranched copolyester-carbonate resins wherein a minor amount (typicallybetween 0.05 and 2 mole percent, based on the quantity of dihydricphenol used) of a polyfunctional aromatic compound is a co-reactant withthe dihydric phenol in the reaction mixture, comprising also thecarbonate precursor and the ester precursor, to provide a thermoplasticrandomly branched copolyester-carbonate. These polyfunctional aromaticcompounds contain at least three functional groups which may behydroxyl, carboxyl, carboxylic anhydride, haloformyl, or mixturesthereof. Some illustrative non-limiting examples of these polyfunctionalcompounds include trimellitic anhydride, trimellitic acid, trimellityltrichloride, 4-chloroformyl phthalic anhydride, pyromellitic acid,pyromellitic dianhydride, mellitic acid, mellitic anhydride, trimesicacid, benzophenonetetracarboxylic acid, benzophenonetetracarboxylic acidanhydride, and the like. Other organic polyfunctional compounds usefulin making these randomly branched copolyester-carbonates are disclosedin U.S. Pat. Nos. 3,635,895 and 4,001,184, both of which areincorporated herein by reference.

The proportions of reactants employed to prepare thecopolyester-carbonate resins subjected to thermal degredation to obtainresins of the invention containing a unit of the formula (I) given abovewill vary in accordance with the proposed use of the product resin. Whenthe product resin containing the divalent moieties of the formula Igiven above is to be used as an intermediate in the preparation of abranched, essentially thermoplastic resin, the dihydric phenol andcarbonate precursor are advantageously employed in substantiallyequivalent molar proportions and from about 0.1 to 1.0 mole percent ofthe dicarboxylic acid of formula II is employed. When the product resincontaining the divalent moieties of the formula I given above is to beused as an intermediate in the preparation of a cross-linked resin, fromabout 1.0 to about 25 mole percent of the dicarboxylic acid of formulaII is employed. For these resins proportionally less of the carbonateprecursor may be used to allow for replacement of carbonate units bydicarboxylic acid units in the polymer chain. In the precedingdiscussion, mole percent is defined as moles of dicarboxylic aciddivided by moles of bisphenol multiplied by 100.

The copolyester-carbonate resins described above as precursors for theresins of the invention containing the polymer units of formula (I)given above are converted to the resins of the invention by thermaldegradation, i.e.; exposure to temperatures of 100° to 350° C.,preferably 200° to 300 ° C. for a period of time sufficient to effectremoval of the R group. Under the conditions of the thermolyticdegradation to remove the R groups (see Formula IIA and IIB) the unitsof formula (I) are formed, creating a cross-linking site (a carboxylgroup-bearing moiety), the transitory resin intermediate of theinvention. The active crossing-link site may immediately react tocross-link with an adjacent polycarbonate or copolyester-carbonate resinchain.

This is believed to occur by reaction of the free CO₂ H group with acarbonate or ester functional group in a repeat unit of the resin chain.

The resins of the invention may be used in admixture with previouslyknown polycarbonates and copolyester-carbonates as branching orcross-linking agents by admixture of the precursor resin containing Rgroups with the polycarbonate or copolyester-carbonate to be branched orcross-linked, and forming the resin containing the units of formula (I)in-situ.

The thermoplastic molding resin compositions of the instant inventioncontaining units of the formula (I) or its precursor resin may also beadmixed with various commonly known and used additives such as, forexample, antioxidants; antistatic agents; inert fillers such as glass,talc, mica, and clay; ultraviolet radiation absorbers such as thebenzophenones, benzotriazoles, and the like; hydrolytic stabilizers suchas the epoxides disclosed in U.S. Pat. Nos. 3,489,716, 4,138,379 and3,839,247, all of which are incorporated herein by reference; colorstabilizers such as the organophosphites; thermal stabilizers such as aphosphite; flame retardants; and mold release agents. A wide variety offlame retardancy additives useful in polycarbonate andcopolyester-carbonate resin compositions are known and may be employedherein.

Some particularly useful flame retardants are the alkali and alkalineearth metal salts of sulfonic acids. These types of flame retardants aredisclosed in U.S. Pat. Nos. 3,933,734; 3,931,100; 3,978,024; 3,948,851;3,926,980; 3,919,167; 3,909,490; 3,953,396; 3,953,300; 3,917,559;3,951,910 and 3,940,366, all of which are hereby incorporated herein byreference.

The following examples and preparations describe the manner and processof making and using the invention and set forth the best modecontemplated by the inventor of carrying out the invention but are notto be construed as limiting the invention. Where reported, the followingtests were carried out.

Intrinsic Viscosity

The intrinsic viscosity was measured at a temperature of 25° C. inmethylene chloride and is reported in deciliters/gram (dl/g).

Degree of Cross-Linking (gel formation)

5 grams of the resin is placed in a Petri dish and dried for 4 hours ata temperature of 110° C. The dish is then placed in a vacuum oven andheated to a temperature of 300° C. under a vacuum of about 5 mm Hg for0.5 hours or 1 hour. The percentage of gel content is then determined bysoaking the resin sample in methylene chloride for 24 hours, washing thesoaked material thoroughly with additional methylene chloride anddetermining the residual weight. The percentage of gel is the residualweight divided by the original weight of the heat-aged material.

Preparation 1

To a suitable reaction vessel there is charged trimellitic anhydride anda 2.5X molar excess of isopropyl alcohol. The charge is heated to refluxtemperature for about one hour. At the end of this time period analiquot of the reaction mixture shows an absence of anhydride (byinfra-red analysis). Residual unreacted isopropyl alcohol was removed ona rotary evaporator. The product is the isopropyl alcohol monoester of1,2,4-benzene tricarboxylic acid.

EXAMPLE 1 (COMPARATIVE EXAMPLE)

This example is not an example of the invention but is made forcomparative purposes.

A reactor vessel fitted with a mechanical agitator is charged with 560ml of deionized water, 680 ml of methylene chloride, 114 g (0.5 moles)of bisphenol-A, 2.8 ml (0.02 mole) of triethylamine and 2.3 g (0.025moles) of phenol. Phosgene is introduced into the charge while thecharge is agitated. Phosgene is added at a rate of 1 g/minute for 60minutes (0.6 moles) while the pH of the resulting reaction mixture ismaintained between 9.5 and 11.5. The pH was adjusted to 11 at the end ofthe reaction. The pH adjustments are made by the addition of 25% aqueoussodium hydroxide. After phosgenation has been terminated, the brinelayer is separated from the resin solution and the resin solution iswashed with 3 weight percent aqueous HCl and with water. The resin isthen precipitated and isolated by addition of the resin solution to 3000ml methanol in a Waring blender.

Representative portions of the resin are subjected to thermolysis andanalysis to determine the degree of cross-linking by the proceduredescribed above. The analytical results are shown in the table, below.

EXAMPLE 2

The procedure of Example 1, supra., is repeated except that there isalso included in the reaction vessel charge 6.3 g (0.025 moles) of theisopropyl alcohol monoester of 1,2,4-benzene tricarboxylic acid preparedin accordance with the procedure of Preparation 1, supra. Also, the pHof the reaction mixture is maintained at a pH of from 5 to 7 for thefirst 7 minutes after phosgenation is initiated and then at the pH offrom 9.5 to 11.5 for 60 minutes. The resin obtained has pendantOCH(CH₃)₂ groups. The resin is subjected to thermolysis for 1/2 hour and1 hour to convert the OCH(CH₃)₂ groups to functional COOH groups, whichthen in turn crosslink the resin. The results are given in the table,below.

EXAMPLE 3

The procedure of Example 2, supra., is repeated except that theproportion of phenol is increased to 4.6 g (0.05 moles), the proportionof monoester is increased to 12.6 g (0.05 moles) and an initial periodof phosgenation for 14 minutes was followed by 60 minutes at a pH of 9.5to 11.5. The analytical results are shown in the table, below.

EXAMPLE 4

The procedure of Example 2, supra., is repeated except that theproportion of monoester is increased to 12.6 g (0.05 moles) and aninitial phosgenation period of 14 minutes was followed by 60 minutes ofphosgenation at a pH of 9.5 to 11.5. The analytical results are shownbelow.

                  TABLE                                                           ______________________________________                                        Ex-                     Percent Gels                                          am-  Mole     Mole      After 300° C./5 mm                                                                 IV                                        ple  Percent  Percent   Thermolysis Before                                    No.  Phenol   Monoester 0.5 hr.                                                                              1 hr.  Thermolysis                             ______________________________________                                        1    5        0 (Control)                                                                              3      3     0.388                                   2    5        5         61     84     0.376                                   3    10       10         8     96     0.265                                   4    5        10        86     81     0.378                                   ______________________________________                                    

What is claim:
 1. A thermoplastic polyester-carbonate resin containingin the polymer chain, at least one divalent moiety selected from thoseof the formulae: ##STR9##
 2. A thermoplastic polyester-carbonate resincontaining in the polymer chain, at least one divalent moiety selectedfrom those of the formulae: ##STR10## wherein R is a hydrocarbyl groupselected from alkyl or cycloalkyl groups amenable to removal by thermaldegradation.
 3. The resin of claim 2 in admixture with a flame retardingproportion of a flame retardant.
 4. The resin of claim 2 folowingthermal degradation to remove the hydrocarbyl group and cross-linking ofadjacent resin chains.
 5. The admixture of claim 3 wherein the resin hasbeen thermally degraded to remove the hydrocarbyl group and adjacentresin chains are cross-linked.